1. Field of the Invention
The present invention relates to an encoding method and system, and more particularly, to fast encoding method and system that can transmit video data in real time using adaptive intra prediction in accordance with the H.264/AVC (Advanced Video Codec) standard so as to efficiently provide security-related images or multimedia images in various network environments with high quality.
2. Description of the Related Art
The requirement for high-performance video compression techniques for efficiently providing a multimedia service in various network environments has increased. In the field of security, much attention has been paid to real-time transmission of high-quality images in networks with consumers' requirements.
The VCEG (Video Coding Experts Group) of the ITU-T and the MPEG (Moving Picture Expert Group) of the ISO/IEC established the MPEG-4 Part 10/H.264 standard for improving the network adaptiveness and the error resilience to provide high-quality images. In the present field of security, the replacement with the H.264/AVC compression scheme providing compression performance 30 to 40 times higher than that of the MPEG-4 scheme or the MJPEG scheme which is the primary compression scheme of DVRs or IP (Internet Protocol) cameras has been strongly requested for. Accordingly, in view of flexibility for easy adaptation to various network environments and encoding efficiency of moving images, studies for replacement with the H.264/AVC which is the next-generation moving image compression standard much advanced from the existing standards have been actively made.
According to the H.264/AVC, it is possible to accomplish video compression with high quality at a bit rate lower than that of the existing encoding schemes such as the MPEG-2 and the H.263. This is because of the use of intra/inter prediction schemes which is more various and complex than the existing schemes. As a result, the compression efficiency has been improved but more calculation and access to memory than those of the existing schemes have been required. Therefore, there is a need for studies for improving encoding performance by reducing the complexity of the encoder while maintaining the quality of images in the applications requiring the real-time transmission. Particularly, the encoding scheme using H.264 intra prediction is a technique as a spatial prediction scheme suggested for removing the spatial overlap using pixels of the peripheral blocks around pixels in the present block in the same image. This scheme minimizes error signals as an actual encoding target to improve the compression performance by using plural prediction modes with spatial directivity. The SAD (Sum of Absolute Differences) or the SATD (Sum of Absolute Transform Difference) between various predicted blocks and the original block is calculated and then a mode having the smallest value is selected as the optimal prediction mode. That is, in this scheme, since thirteen modes in total of nine modes for 4×4 brightness blocks and four modes for 16×16 brightness blocks are entirely retrieved at the time of determining the macro block prediction mode and then the mode having the minimum prediction error is selected, the calculation quantity is made to greatly increase and thus the processing time is also made to increase.
Various methods for reducing the calculation quantity of the H.264 intra encoding prediction scheme have been developed. The developed fast intra prediction mode determining methods include an edge map method of selecting one mode from various modes based on an edge direction, an EIP (Efficient Intra Prediction) method of detecting a specific condition and determining a mode satisfying the detected specific condition, a Pan algorithm of normalizing similar edge values between brightness components and chrominance components and determining a mode, a 4×4 mode determining method using the block size determination skip and the directivity, and a method using a Sober filter and a histogram in the edge direction. However, in such methods, the calculation quality is reduced in comparison with the existing entire mode retrieval method, but additional calculations for determining a new mode is required. Accordingly, in a multi-channel image security system, there is a need for more reducing the complexity and the calculation quantity for real-time operation.